The permission is granted by your government. Either move to a libertarian paradise where 10 year olds can drink or accept that a merchant will apply measures to protect their liquor license.
Far more harmful is self-checkout without a discount for free labor or treating your customers like criminals when they leave the store with their own property.
I'm saying that regulatory requirements should be less strict, so that retailers are not turned into an extension of the government. Many developed countries establish a minimum age for alcohol purchase but don't build unwieldy infrastructures around it, relying instead on the aggregate judgement of their populace.
You seem to have missed the part where I do not want to ask permission of the government for every little thing. I'm well into middle age and do not appreciate having to seek governmental approval for what I consume. I am fine with some products like alcohol being subjected to taxes to balance out negative externalities. I am not fine with the idea of showing my papers on demand.
Far more harmful is self-checkout without a discount for free labor or treating your customers like criminals when they leave the store with their own property.